Pharmacy benefit managers (PBMs) administer prescription drug benefits for insurers, employers, and other payers through formulary design, rebate negotiation, pharmacy network management, and utilization controls. In diabetes care, cost-containment strategies such as formulary-driven medication switching, step therapy, and formulary exclusivity have increasingly restricted access to essential medications and technologies. These rebate-driven practices often prioritize financial incentives over clinical appropriateness, leading to forced nonmedical switching, higher out-of-pocket costs, reduced adherence, and poorer glycemic outcomes. This narrative review examines how PBM-driven policies undermine patient-centered, evidence-based diabetes care and disrupt continuity of treatment. Greater transparency, preservation of patient and clinician choice, and policies that align PBM incentives with clinical outcomes are needed to reduce harm and improve access to appropriate diabetes therapies.